--- //depot/vendor/freebsd/src/sys/amd64/acpica/acpi_machdep.c
+++ //depot/projects/multipass/sys/amd64/acpica/acpi_machdep.c
@@ -360,7 +360,7 @@
 
 	nexus_init_resources();
 	bus_generic_probe(dev);
-	acpi_dev = BUS_ADD_CHILD(dev, 10, "acpi", 0);
+	acpi_dev = BUS_ADD_CHILD(dev, 0, "acpi", 0);
 	if (acpi_dev == NULL)
 		panic("failed to add acpi0 device");
 
@@ -382,4 +382,5 @@
 DEFINE_CLASS_1(nexus, nexus_acpi_driver, nexus_acpi_methods, 1, nexus_driver);
 static devclass_t nexus_devclass;
 
-DRIVER_MODULE(nexus_acpi, root, nexus_acpi_driver, nexus_devclass, 0, 0);
+EARLY_DRIVER_MODULE(nexus_acpi, root, nexus_acpi_driver, nexus_devclass, 0, 0,
+    BUS_PASS_BUS);
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi.c
@@ -227,7 +227,8 @@
 };
 
 static devclass_t acpi_devclass;
-DRIVER_MODULE(acpi, nexus, acpi_driver, acpi_devclass, acpi_modevent, 0);
+EARLY_DRIVER_MODULE(acpi, nexus, acpi_driver, acpi_devclass, acpi_modevent, 0,
+    BUS_PASS_BUS);
 MODULE_VERSION(acpi, 1);
 
 ACPI_SERIAL_DECL(acpi, "ACPI root bus");
@@ -1817,29 +1818,17 @@
 static void
 acpi_probe_order(ACPI_HANDLE handle, int *order)
 {
-	ACPI_OBJECT_TYPE type;
 
 	/*
-	 * 0. CPUs
-	 * 1. I/O port and memory system resource holders
 	 * 2. Clocks and timers (to handle early accesses)
 	 * 3. Embedded controllers (to handle early accesses)
-	 * 4. PCI Link Devices
 	 */
-	AcpiGetType(handle, &type);
-	if (type == ACPI_TYPE_PROCESSOR)
-		*order = 0;
-	else if (acpi_MatchHid(handle, "PNP0C01") ||
-	    acpi_MatchHid(handle, "PNP0C02"))
-		*order = 1;
-	else if (acpi_MatchHid(handle, "PNP0100") ||
+	if (acpi_MatchHid(handle, "PNP0100") ||
 	    acpi_MatchHid(handle, "PNP0103") ||
 	    acpi_MatchHid(handle, "PNP0B00"))
 		*order = 2;
 	else if (acpi_MatchHid(handle, "PNP0C09"))
 		*order = 3;
-	else if (acpi_MatchHid(handle, "PNP0C0F"))
-		*order = 4;
 }
 
 /*
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_cpu.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_cpu.c
@@ -208,7 +208,8 @@
 };
 
 static devclass_t acpi_cpu_devclass;
-DRIVER_MODULE(cpu, acpi, acpi_cpu_driver, acpi_cpu_devclass, 0, 0);
+EARLY_DRIVER_MODULE(cpu, acpi, acpi_cpu_driver, acpi_cpu_devclass, 0, 0,
+    BUS_PASS_CPU);
 MODULE_DEPEND(cpu, acpi, 1, 1, 1);
 
 static int
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_ec.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_ec.c
@@ -263,7 +263,8 @@
 };
 
 static devclass_t acpi_ec_devclass;
-DRIVER_MODULE(acpi_ec, acpi, acpi_ec_driver, acpi_ec_devclass, 0, 0);
+EARLY_DRIVER_MODULE(acpi_ec, acpi, acpi_ec_driver, acpi_ec_devclass, 0, 0,
+    BUS_PASS_SCHEDULER);
 MODULE_DEPEND(acpi_ec, acpi, 1, 1, 1);
 
 /*
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_hpet.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_hpet.c
@@ -857,5 +857,6 @@
 	sizeof(struct hpet_softc),
 };
 
-DRIVER_MODULE(hpet, acpi, hpet_driver, hpet_devclass, 0, 0);
+EARLY_DRIVER_MODULE(hpet, acpi, hpet_driver, hpet_devclass, 0, 0,
+    BUS_PASS_TIMER);
 MODULE_DEPEND(hpet, acpi, 1, 1, 1);
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_isab.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_isab.c
@@ -85,7 +85,8 @@
 	sizeof(struct acpi_isab_softc),
 };
 
-DRIVER_MODULE(acpi_isab, acpi, acpi_isab_driver, isab_devclass, 0, 0);
+EARLY_DRIVER_MODULE(acpi_isab, acpi, acpi_isab_driver, isab_devclass, 0, 0,
+    BUS_PASS_BUS);
 MODULE_DEPEND(acpi_isab, acpi, 1, 1, 1);
 
 static int
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_pci.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_pci.c
@@ -105,7 +105,8 @@
 
 DEFINE_CLASS_1(pci, acpi_pci_driver, acpi_pci_methods, sizeof(struct pci_softc),
     pci_driver);
-DRIVER_MODULE(acpi_pci, pcib, acpi_pci_driver, pci_devclass, 0, 0);
+EARLY_DRIVER_MODULE(acpi_pci, pcib, acpi_pci_driver, pci_devclass, 0, 0,
+    BUS_PASS_BUS);
 MODULE_DEPEND(acpi_pci, acpi, 1, 1, 1);
 MODULE_DEPEND(acpi_pci, pci, 1, 1, 1);
 MODULE_VERSION(acpi_pci, 1);
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_pci_link.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_pci_link.c
@@ -1118,6 +1118,6 @@
 
 static devclass_t pci_link_devclass;
 
-DRIVER_MODULE(acpi_pci_link, acpi, acpi_pci_link_driver, pci_link_devclass, 0,
-    0);
+EARLY_DRIVER_MODULE(acpi_pci_link, acpi, acpi_pci_link_driver,
+    pci_link_devclass, 0, 0, BUS_PASS_INTERRUPT);
 MODULE_DEPEND(acpi_pci_link, acpi, 1, 1, 1);
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_pcib_acpi.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_pcib_acpi.c
@@ -140,7 +140,8 @@
 
 DEFINE_CLASS_0(pcib, acpi_pcib_acpi_driver, acpi_pcib_acpi_methods,
     sizeof(struct acpi_hpcib_softc));
-DRIVER_MODULE(acpi_pcib, acpi, acpi_pcib_acpi_driver, pcib_devclass, 0, 0);
+EARLY_DRIVER_MODULE(acpi_pcib, acpi, acpi_pcib_acpi_driver, pcib_devclass, 0, 0,
+    BUS_PASS_BUS);
 MODULE_DEPEND(acpi_pcib, acpi, 1, 1, 1);
 
 static int
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_pcib_pci.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_pcib_pci.c
@@ -90,7 +90,8 @@
 
 DEFINE_CLASS_1(pcib, acpi_pcib_pci_driver, acpi_pcib_pci_methods,
     sizeof(struct acpi_pcib_softc), pcib_driver);
-DRIVER_MODULE(acpi_pcib, pci, acpi_pcib_pci_driver, pcib_devclass, 0, 0);
+EARLY_DRIVER_MODULE(acpi_pcib, pci, acpi_pcib_pci_driver, pcib_devclass, 0, 0,
+    BUS_PASS_BUS);
 MODULE_DEPEND(acpi_pcib, acpi, 1, 1, 1);
 
 static int
--- //depot/vendor/freebsd/src/sys/dev/acpica/acpi_resource.c
+++ //depot/projects/multipass/sys/dev/acpica/acpi_resource.c
@@ -636,8 +636,8 @@
 };
 
 static devclass_t acpi_sysres_devclass;
-DRIVER_MODULE(acpi_sysresource, acpi, acpi_sysres_driver, acpi_sysres_devclass,
-    0, 0);
+EARLY_DRIVER_MODULE(acpi_sysresource, acpi, acpi_sysres_driver,
+    acpi_sysres_devclass, 0, 0, BUS_PASS_RESOURCE - 1);
 MODULE_DEPEND(acpi_sysresource, acpi, 1, 1, 1);
 
 static int
--- //depot/vendor/freebsd/src/sys/dev/ctau/if_ct.c
+++ //depot/projects/multipass/sys/dev/ctau/if_ct.c
@@ -339,8 +339,7 @@
 {
 	struct resource *res;
 	
-	if (!(res = bus_alloc_resource (dev, type, &rid, start, end, count,
-	    RF_ALLOCATED)))
+	if (!(res = bus_alloc_resource (dev, type, &rid, start, end, count, 0)))
 		return 0;
 		
 	bus_release_resource (dev, type, rid, res);
--- //depot/vendor/freebsd/src/sys/dev/cx/if_cx.c
+++ //depot/projects/multipass/sys/dev/cx/if_cx.c
@@ -426,8 +426,7 @@
 {
 	struct resource *res;
 	
-	if (!(res = bus_alloc_resource (dev, type, &rid, start, end, count,
-	    RF_ALLOCATED)))
+	if (!(res = bus_alloc_resource (dev, type, &rid, start, end, count, 0)))
 		return 0;
 		
 	bus_release_resource (dev, type, rid, res);
--- //depot/vendor/freebsd/src/sys/dev/digi/digi_isa.c
+++ //depot/projects/multipass/sys/dev/digi/digi_isa.c
@@ -292,7 +292,7 @@
 	/* Temporarily map our memory */
 	sc->res.mrid = 0;
 	sc->res.mem = bus_alloc_resource(dev, SYS_RES_MEMORY, &sc->res.mrid,
-	    0ul, ~0ul, sc->win_size, RF_ALLOCATED);
+	    0ul, ~0ul, sc->win_size, 0);
 	if (sc->res.mem == NULL) {
 		device_printf(dev, "0x%lx: Memory range is in use\n", sc->pmem);
 		bus_release_resource(dev, SYS_RES_IOPORT, sc->res.iorid,
--- //depot/vendor/freebsd/src/sys/dev/pci/eisa_pci.c
+++ //depot/projects/multipass/sys/dev/pci/eisa_pci.c
@@ -73,7 +73,8 @@
 
 static devclass_t eisab_devclass;
 
-DRIVER_MODULE(eisab, pci, eisab_driver, eisab_devclass, 0, 0);
+EARLY_DRIVER_MODULE(eisab, pci, eisab_driver, eisab_devclass, 0, 0,
+    BUS_PASS_BUS);
 
 static int
 eisab_probe(device_t dev)
--- //depot/vendor/freebsd/src/sys/dev/pci/hostb_pci.c
+++ //depot/projects/multipass/sys/dev/pci/hostb_pci.c
@@ -264,4 +264,5 @@
 
 static devclass_t pci_hostb_devclass;
 
-DRIVER_MODULE(hostb, pci, pci_hostb_driver, pci_hostb_devclass, 0, 0);
+EARLY_DRIVER_MODULE(hostb, pci, pci_hostb_driver, pci_hostb_devclass, 0, 0,
+    BUS_PASS_BUS);
--- //depot/vendor/freebsd/src/sys/dev/pci/isa_pci.c
+++ //depot/projects/multipass/sys/dev/pci/isa_pci.c
@@ -93,7 +93,7 @@
     sizeof(struct isab_pci_softc),
 };
 
-DRIVER_MODULE(isab, pci, isab_driver, isab_devclass, 0, 0);
+EARLY_DRIVER_MODULE(isab, pci, isab_driver, isab_devclass, 0, 0, BUS_PASS_BUS);
 
 /*
  * XXX we need to add a quirk list here for bridges that don't correctly
--- //depot/vendor/freebsd/src/sys/dev/pci/pci.c
+++ //depot/projects/multipass/sys/dev/pci/pci.c
@@ -182,7 +182,8 @@
 DEFINE_CLASS_0(pci, pci_driver, pci_methods, sizeof(struct pci_softc));
 
 static devclass_t pci_devclass;
-DRIVER_MODULE(pci, pcib, pci_driver, pci_devclass, pci_modevent, NULL);
+EARLY_DRIVER_MODULE(pci, pcib, pci_driver, pci_devclass, pci_modevent, NULL,
+    BUS_PASS_BUS);
 MODULE_VERSION(pci, 1);
 
 static char	*pci_vendordata;
--- //depot/vendor/freebsd/src/sys/dev/pci/pci_pci.c
+++ //depot/projects/multipass/sys/dev/pci/pci_pci.c
@@ -100,7 +100,8 @@
 static devclass_t pcib_devclass;
 
 DEFINE_CLASS_0(pcib, pcib_driver, pcib_methods, sizeof(struct pcib_softc));
-DRIVER_MODULE(pcib, pci, pcib_driver, pcib_devclass, NULL, NULL);
+EARLY_DRIVER_MODULE(pcib, pci, pcib_driver, pcib_devclass, NULL, NULL,
+    BUS_PASS_BUS);
 
 #ifdef NEW_PCIB
 
--- //depot/vendor/freebsd/src/sys/dev/pci/vga_pci.c
+++ //depot/projects/multipass/sys/dev/pci/vga_pci.c
@@ -604,4 +604,5 @@
 
 static devclass_t vga_devclass;
 
-DRIVER_MODULE(vgapci, pci, vga_pci_driver, vga_devclass, 0, 0);
+EARLY_DRIVER_MODULE(vgapci, pci, vga_pci_driver, vga_devclass, 0, 0,
+    BUS_PASS_BUS);
--- //depot/vendor/freebsd/src/sys/i386/acpica/acpi_machdep.c
+++ //depot/projects/multipass/sys/i386/acpica/acpi_machdep.c
@@ -375,7 +375,7 @@
 
 	nexus_init_resources();
 	bus_generic_probe(dev);
-	if (BUS_ADD_CHILD(dev, 10, "acpi", 0) == NULL)
+	if (BUS_ADD_CHILD(dev, 0, "acpi", 0) == NULL)
 		panic("failed to add acpi0 device");
 
 	return (bus_generic_attach(dev));
@@ -392,4 +392,5 @@
 DEFINE_CLASS_1(nexus, nexus_acpi_driver, nexus_acpi_methods, 1, nexus_driver);
 static devclass_t nexus_devclass;
 
-DRIVER_MODULE(nexus_acpi, root, nexus_acpi_driver, nexus_devclass, 0, 0);
+EARLY_DRIVER_MODULE(nexus_acpi, root, nexus_acpi_driver, nexus_devclass, 0, 0,
+    BUS_PASS_BUS);
--- //depot/vendor/freebsd/src/sys/i386/bios/smapi.c
+++ //depot/projects/multipass/sys/i386/bios/smapi.c
@@ -162,7 +162,7 @@
 		rid = 0;
 		length = ADDR2HDR(addr)->length;
 
-		child = BUS_ADD_CHILD(parent, 5, "smapi", -1);
+		child = BUS_ADD_CHILD(parent, 0, "smapi", -1);
 		device_set_driver(child, driver);
 		bus_set_resource(child, SYS_RES_MEMORY, rid, addr, length);
 		device_set_desc(child, "SMAPI BIOS");
--- //depot/vendor/freebsd/src/sys/i386/pci/pci_pir.c
+++ //depot/projects/multipass/sys/i386/pci/pci_pir.c
@@ -752,4 +752,10 @@
 
 static devclass_t pir_devclass;
 
-DRIVER_MODULE(pir, legacy, pir_driver, pir_devclass, 0, 0);
+/*
+ * XXX: This has to be BUS_PASS_BUS for now.  It should really be
+ * BUS_PASS_INTERRUPT, but we can't do that until we rework PCI to
+ * not route interrupts until after BUS_PASS_INTERRUPT.
+ */
+EARLY_DRIVER_MODULE(pir, legacy, pir_driver, pir_devclass, 0, 0,
+    BUS_PASS_BUS);
--- //depot/vendor/freebsd/src/sys/ia64/ia64/nexus.c
+++ //depot/projects/multipass/sys/ia64/ia64/nexus.c
@@ -148,7 +148,8 @@
 };
 static devclass_t nexus_devclass;
 
-DRIVER_MODULE(nexus, root, nexus_driver, nexus_devclass, 0, 0);
+EARLY_DRIVER_MODULE(nexus, root, nexus_driver, nexus_devclass, 0, 0,
+    BUS_PASS_BUS);
 
 static int
 nexus_probe(device_t dev)
--- //depot/vendor/freebsd/src/sys/isa/pnp.c
+++ //depot/projects/multipass/sys/isa/pnp.c
@@ -824,4 +824,4 @@
 
 static devclass_t pnp_devclass;
 
-DRIVER_MODULE(pnp, isa, pnp_driver, pnp_devclass, 0, 0);
+EARLY_DRIVER_MODULE(pnp, isa, pnp_driver, pnp_devclass, 0, 0, BUS_PASS_BUS);
--- //depot/vendor/freebsd/src/sys/x86/bios/smbios.c
+++ //depot/projects/multipass/sys/x86/bios/smbios.c
@@ -102,7 +102,7 @@
 				return;
 		}
 
-		child = BUS_ADD_CHILD(parent, 5, "smbios", -1);
+		child = BUS_ADD_CHILD(parent, 0, "smbios", -1);
 		device_set_driver(child, driver);
 		bus_set_resource(child, SYS_RES_MEMORY, rid, addr, length);
 		device_set_desc(child, "System Management BIOS");
--- //depot/vendor/freebsd/src/sys/x86/bios/vpd.c
+++ //depot/projects/multipass/sys/x86/bios/vpd.c
@@ -128,7 +128,7 @@
 		rid = 0;
 		length = ADDR2VPD(addr)->Length;
 
-		child = BUS_ADD_CHILD(parent, 5, "vpd", -1);
+		child = BUS_ADD_CHILD(parent, 0, "vpd", -1);
 		device_set_driver(child, driver);
 		bus_set_resource(child, SYS_RES_MEMORY, rid, addr, length);
 		device_set_desc(child, "Vital Product Data Area");
--- //depot/vendor/freebsd/src/sys/x86/isa/orm.c
+++ //depot/projects/multipass/sys/x86/isa/orm.c
@@ -182,4 +182,5 @@
 
 static devclass_t orm_devclass;
 
-DRIVER_MODULE(orm, isa, orm_driver, orm_devclass, 0, 0);
+EARLY_DRIVER_MODULE(orm, isa, orm_driver, orm_devclass, 0, 0,
+    BUS_PASS_RESOURCE);
--- //depot/vendor/freebsd/src/sys/x86/pci/pci_bus.c
+++ //depot/projects/multipass/sys/x86/pci/pci_bus.c
@@ -458,12 +458,7 @@
 
 			if (s == NULL)
 				continue;
-			/*
-			 * Add at priority 100 to make sure we
-			 * go after any motherboard resources
-			 */
-			child = BUS_ADD_CHILD(parent, 100,
-					      "pcib", busnum);
+			child = BUS_ADD_CHILD(parent, 0, "pcib", busnum);
 			device_set_desc(child, s);
 			legacy_set_pcibus(child, busnum);
 			legacy_set_pcislot(child, slot);
@@ -490,7 +485,7 @@
 		if (bootverbose)
 			printf(
 	"legacy_pcib_identify: no bridge found, adding pcib0 anyway\n");
-		child = BUS_ADD_CHILD(parent, 100, "pcib", 0);
+		child = BUS_ADD_CHILD(parent, 0, "pcib", 0);
 		legacy_set_pcibus(child, 0);
 	}
 }
@@ -639,7 +634,8 @@
 static devclass_t hostb_devclass;
 
 DEFINE_CLASS_0(pcib, legacy_pcib_driver, legacy_pcib_methods, 1);
-DRIVER_MODULE(pcib, legacy, legacy_pcib_driver, hostb_devclass, 0, 0);
+EARLY_DRIVER_MODULE(pcib, legacy, legacy_pcib_driver, hostb_devclass, 0, 0,
+    BUS_PASS_BUS);
 
 
 /*
@@ -712,7 +708,8 @@
 
 DEFINE_CLASS_1(pcib, pcibios_pcib_driver, pcibios_pcib_pci_methods,
     sizeof(struct pcib_softc), pcib_driver);
-DRIVER_MODULE(pcibios_pcib, pci, pcibios_pcib_driver, pcib_devclass, 0, 0);
+EARLY_DRIVER_MODULE(pcibios_pcib, pci, pcibios_pcib_driver, pcib_devclass, 0, 0,
+    BUS_PASS_BUS);
 
 static int
 pcibios_pcib_probe(device_t dev)
--- //depot/vendor/freebsd/src/sys/x86/x86/io_apic.c
+++ //depot/projects/multipass/sys/x86/x86/io_apic.c
@@ -856,12 +856,8 @@
 apic_identify(driver_t *driver, device_t parent)
 {
 
-	/*
-	 * Add at order 12.  acpi0 is probed at order 10 and legacy0
-	 * is probed at order 11.
-	 */
 	if (lapic_paddr != 0)
-		BUS_ADD_CHILD(parent, 12, "apic", 0);
+		BUS_ADD_CHILD(parent, 0, "apic", 0);
 }
 
 static int
@@ -921,7 +917,8 @@
 DEFINE_CLASS_0(apic, apic_driver, apic_methods, 0);
 
 static devclass_t apic_devclass;
-DRIVER_MODULE(apic, nexus, apic_driver, apic_devclass, 0, 0);
+EARLY_DRIVER_MODULE(apic, nexus, apic_driver, apic_devclass, 0, 0,
+    BUS_PASS_RESOURCE);
 
 #include "opt_ddb.h"
 
--- //depot/vendor/freebsd/src/sys/x86/x86/legacy.c
+++ //depot/projects/multipass/sys/x86/x86/legacy.c
@@ -108,7 +108,8 @@
 };
 static devclass_t legacy_devclass;
 
-DRIVER_MODULE(legacy, nexus, legacy_driver, legacy_devclass, 0, 0);
+EARLY_DRIVER_MODULE(legacy, nexus, legacy_driver, legacy_devclass, 0, 0,
+    BUS_PASS_BUS);
 
 static int
 legacy_probe(device_t dev)
@@ -296,7 +297,7 @@
 	1,		/* no softc */
 };
 static devclass_t cpu_devclass;
-DRIVER_MODULE(cpu, legacy, cpu_driver, cpu_devclass, 0, 0);
+EARLY_DRIVER_MODULE(cpu, legacy, cpu_driver, cpu_devclass, 0, 0, BUS_PASS_CPU);
 
 static void
 cpu_identify(driver_t *driver, device_t parent)
@@ -304,13 +305,8 @@
 	device_t child;
 	int i;
 
-	/*
-	 * Attach a cpuX device for each CPU.  We use an order of 150
-	 * so that these devices are attached after the Host-PCI
-	 * bridges (which are added at order 100).
-	 */
 	CPU_FOREACH(i) {
-		child = BUS_ADD_CHILD(parent, 150, "cpu", i);
+		child = BUS_ADD_CHILD(parent, 0, "cpu", i);
 		if (child == NULL)
 			panic("legacy_attach cpu");
 	}
--- //depot/vendor/freebsd/src/sys/x86/x86/mptable_pci.c
+++ //depot/projects/multipass/sys/x86/x86/mptable_pci.c
@@ -213,7 +213,8 @@
 
 DEFINE_CLASS_0(pcib, mptable_hostb_driver, mptable_hostb_methods,
     sizeof(struct mptable_hostb_softc));
-DRIVER_MODULE(mptable_pcib, legacy, mptable_hostb_driver, hostb_devclass, 0, 0);
+EARLY_DRIVER_MODULE(mptable_pcib, legacy, mptable_hostb_driver, hostb_devclass,
+    0, 0, BUS_PASS_BUS);
 
 /* PCI to PCI bridge driver. */
 
@@ -248,4 +249,5 @@
 
 DEFINE_CLASS_1(pcib, mptable_pcib_driver, mptable_pcib_pci_methods,
     sizeof(struct pcib_softc), pcib_driver);
-DRIVER_MODULE(mptable_pcib, pci, mptable_pcib_driver, pcib_devclass, 0, 0);
+EARLY_DRIVER_MODULE(mptable_pcib, pci, mptable_pcib_driver, pcib_devclass, 0, 0,
+    BUS_PASS_BUS);
--- //depot/vendor/freebsd/src/sys/x86/x86/nexus.c
+++ //depot/projects/multipass/sys/x86/x86/nexus.c
@@ -177,7 +177,8 @@
 DEFINE_CLASS_0(nexus, nexus_driver, nexus_methods, 1);
 static devclass_t nexus_devclass;
 
-DRIVER_MODULE(nexus, root, nexus_driver, nexus_devclass, 0, 0);
+EARLY_DRIVER_MODULE(nexus, root, nexus_driver, nexus_devclass, 0, 0,
+    BUS_PASS_BUS);
 
 static int
 nexus_probe(device_t dev)
@@ -279,7 +280,7 @@
 	 * types (such as ACPI), use their own nexus(4) subclass
 	 * driver to override this routine and add their own root bus.
 	 */
-	if (BUS_ADD_CHILD(dev, 10, "legacy", 0) == NULL)
+	if (BUS_ADD_CHILD(dev, 0, "legacy", 0) == NULL)
 		panic("legacy: could not attach");
 	bus_generic_attach(dev);
 	return 0;
@@ -772,7 +773,8 @@
 
 static devclass_t ram_devclass;
 
-DRIVER_MODULE(ram, nexus, ram_driver, ram_devclass, 0, 0);
+EARLY_DRIVER_MODULE(ram, nexus, ram_driver, ram_devclass, 0, 0,
+    BUS_PASS_RESOURCE);
 
 #ifdef DEV_ISA
 /*
@@ -821,5 +823,6 @@
 
 static devclass_t sysresource_devclass;
 
-DRIVER_MODULE(sysresource, isa, sysresource_driver, sysresource_devclass, 0, 0);
+EARLY_DRIVER_MODULE(sysresource, isa, sysresource_driver, sysresource_devclass,
+    0, 0, BUS_PASS_RESOURCE - 1);
 #endif /* DEV_ISA */